Re-Roofing Specifications for Concrete Tile

Advantages

• While initially expensive, a concrete tile roof can save money in the long run, especially if used to re-roof a material that may need replacing because it is nearing the end of its durable life. Tile roofs are naturally fireproof, so they can lead to discounts on homeowner insurance. They can reduce energy bills with their insulating, high-thermal mass. They can also increase the value of a home because of their dimensionality and because their surface can receive patterns to duplicate other materials. They require no repainting or maintenance beyond the occasional cleaning or replacement of broken tile.

Origins

• In the past, roofers and manufacturers who worked nationally had to contend with at least three national standards for concrete tile specifications and installations. To counteract the growing inconsistency among construction, the three national standards bodies formed the non-profit International Code Council in 1994. This member body streamlined the existing codes and eliminated conflicts to produce the International Residential Code, which has since become the foundation for nearly all local and state building authorities. Today, a homeowner who moves from New York to Los Angeles can be assured of the same standards of quality at both locations.

Basics

• Concrete tile requires a roof deck that is sloped at a ratio of 2 1/2 units of rise over 12 units of horizontal movement, or 2.5:12. Slopes from this up to 4:12 require double underlayment or lining for maximum moisture protection. Such underlayment must start with a 19-inch strip fastened sufficiently at the eave and continue with 36-inch- wide strips overlapped at 19-inch intervals. For slopes of 4:12 or greater, only one layer of underlayment is needed, applied shingle-style starting at the eaves and lapping every 2 inches. In areas with high winds, underlayment requires corrosion-resistant fasteners applied according to manufacturer’s instructions.

Fasteners

• Fasteners for concrete tile must be corrosion resistant and measure over 11-gauge, with at least a 0.31-inch head. They must penetrate the roof deck a minimum of 0.75 inch or through the entire deck thickness, whichever is smaller. Attachment wire must be at least 0.083 inch. Perimeter fastening areas must include three tile courses that are within 36 inches from either side of the hips, or from the ridges and edges of the eaves.

Flashing

• Where different roof surfaces join, flashing and counterflashing are required to protect the roof deck from moisture penetration. If they are made of metal, they must be at least 0.019 inch thick and corrosion resistant. Flashing at valleys must extend at least 11 inches on either side of the center line and have an integrated splash diverter rib that is at least an inch high.